a) Field of the Invention
The invention is directed to a telescope for geodetic instruments, particularly for video tachymeters or video theodolites, with beam paths used for different purposes.
b) Description of the Related Art
Conventional telescopes of geodetic instruments usually have an objective, a focusing lens which is generally constructed in such a way that a short overall length of the telescope is achieved. These telescopes further comprise a reticle plate and an eyepiece for visual observation of the object. As a rule, these telescopes have a fixed focal length and magnification which are designed in accordance with the requirements of the instrument.
Modem electro-optic tachymeters have, in addition, separate beam paths for distance measurement function and target seeking function, as they are called, these separate beam paths being coupled out of the visible telescope beam path and coupled in in the transmitter. With respect to sensitive target seeking, imaging is generally carried out on the CCD matrix or on the CCD chip of a CCD camera or on a quadrant diode with which a corresponding image evaluation and/or signal evaluation is then carried out.
In order to make possible different image fields, DE-GM 90 07 731 discloses a wide-angle camera and a telecamera placed on a tachymeter telescope, so that the tachymeter can be controlled remotely from an operator device by means of a joystick.
In an arrangement according to EP 0 281 518, the imaging of a reference mark is carried out in the form of a diaphragm outside the visible field of view on the camera to ensure correlation with the sighting axes. For this purpose, the camera is arranged on the telescope, wherein the image is reflected in the camera through a prism and supplementary optics.
A further development of this arrangement is described by Gruhn and Kahmen in a publication for the conference on xe2x80x9cOptical 3-D Measurement Techniques, IIIxe2x80x9d, Vienna, 2 to Oct. 4, 1995, page 256. The CCD camera arranged on the telescope has a second beam path with supplementary wide-angle optics which are separated from the actual telescope optics.
Recording the visual image of the terrain with a CCD camera and displaying it on a screen without using an eyepiece for the sighting and measuring functions presents the following disadvantages:
Because of its necessary large focal length, the telescope of the device has a limited and narrow telescope viewing field which is unsuitable for locating a target in the terrain or makes this considerably more difficult.
In this case, registering a large image section from the terrain is possible only by means of stringing together a plurality of individual images in a time-consuming manner.
Also, an electronic zoom function of the CCD camera would not bring about a substantial improvement.
Accordingly, it is the primary object of the invention to provide a telescope for a geodetic instrument which overcomes these disadvantages and substantially simplifies the construction of a tachymeter by providing a plurality of beam paths.
In accordance with the invention, a telescope for geodetic instrument, comprises an objective and means for generating separate beam paths for target seeking or image detection and for distance measurement. In the beam path for target seeking, a CCD camera with CCD matrix or a position-dependent photoelectric receiver arrangement (quadrant photoreceiver) is provided in a first image plane of the objective. A receiver for distance measurement is located in a second image plane of the objective. The telescope further comprises an evaluating device which is connected with the CCD camera or receiver arrangement for signal evaluation and/or image evaluation. Means are also provided in the telescope for generating a wide-angle beam path.
Accordingly, it is advantageous for purposes of a simple construction when a supplementary objective cooperating with the objective is provided for generating the wide-angle beam path. A suitable individual lens can also be connected with the objective as supplementary objective.
It is advantageous when means for imaging the wide-angle beam path and the beam path for target seeking are provided in a common focal plane or image plane. A CCD matrix of a CCD camera and/or a photoelectric receiver arrangement are/is located in this common image plane.
To enable simple switching between the wide-angle beam path and the beam path for target seeking, it is advantageous when a switchable diaphragm is arranged in front of this common image plane. This switchable diaphragm causes an alternating stopping down of these beam paths by displacement in a plane parallel to the common image plane.
Accordingly, it is also advantageous when an optical element which acts as a selective mirror and reflects a portion of the light passing the objective is arranged between the objective and the second image plane of the objective to generate the beam path for target seeking.
A simple construction is provided in that an element which deflects the wide-angle beam path and, after reflection at the selective mirror, the beam path for target seeking relative to the first image plane is arranged between the objective and the selective mirror.
Further, it is advantageous when the CCD matrix and/or the receiver arrangement are/is arranged so as to be adjustable in the direction of the optical axis of the wide-angle beam path or the beam path for target seeking for purposes of carrying out focusing.
The invention will be described more fully in the following with reference to an embodiment example.